This invention relates to steel rule die cutting and more particularly to an improved multi-cavity die with movable and adjustable cutting units which can be easily and precisely spaced relative to each other and which provide even and consistent cuts.
Steel rule dies are commonly used for cutting cloth and cloth-like substances such as natural textiles and synthetic materials like vinyl. Steel rule dies are particularly advantageous in the repetitive cutting of a specific shape for use in clothing, furniture, shoes, and automotive trim panels. In brief, a steel rule cutting die typically comprises a base substrate or backing board in which grooves are cut and lengths of sharpened blade, known as steel rule, are formed to the same shape as the grooves and inserted in the grooves. The grooves are cut in the substrate in the pattern that is desired to be cut out of the material. Thus, when the steel rules are placed into the grooves, they form cutting edges in the shape of the desired patterns. These dies are used together with a cutting press that forces them against and into a stack of material in order to cut the material. Multiple layers of material can be cut with one pressing operation. Typically, one die will include several cutting unit cavities, each with a different pattern and defined by a closed length of rules that several multiple patterns can be cut during a single pass through the press. Multiple cavities on a single die are nested together in an efficient configuration to minimize scrap material.
One problem with typical steel rule dies is that, once the groove is cut into the substrate and the steel rule is placed into the groove, the cavities are permanently arranged in the die. If the pattern of one cavity needs to be modified in any respect, it is necessary to construct a completely new die at significant expense. In other words, there is no flexibility to change the patterns without performing the costly and time consuming procedure of making a whole new die. Additionally, the forces created on such a steel rule during cutting are concentrated on the narrow surface area of the rule that contacts the substrate. As a result, the steel rule is driven into the substrate during cutting operations until it can no longer perform a cutting function. Moreover, the rule can be torqued and damaged when the forces are unevenly distributed along the steel rule and only a portion of the rule is driven into the substrate.
A previous attempt at solving these problems is described in U.S. patent application Ser. No. 08/949,855 now U.S Pat. No. 5,983,766, entitled xe2x80x9cSteel Rule Die with Removable Cutting Units and Method for Using Samexe2x80x9d which is herein incorporated by reference. The application discloses a die which provides flexibility in die cutting patterns by making the cavities part of different cutting units that are separate from, and removably attached to, a substrate. Removal of the cutting units from the primary substrate allows cleaning of scrap material and allows the shape of the cavities to be modified. However, when the cutting units are positioned on the substrate, the spacing between steel rules of the adjacent cutting units is not controlled, and in some instances, the steel rules of adjacent cutting units may be touching each other. Under this arrangement there is a possibility that scrap material can become lodged between and deform the adjacent lengths of the steel rules.
Large cutting dies used particularly in the automotive industry contain a primary substrate made of high grade plywood. The reasons for using plywood include that it is readily available, relatively inexpensive, light weight and easily maneuvered. However, as discussed above, positioning a steel rule with a very small surface area directly on a softer wooden substrate can result in problems, such as the steel rule diving into the wooden substrate under the loads created during cutting. As a result, the height of the steel rule will decrease and eventually the die will stop cutting. This requires that the cavities be moved to another place on the substrate, thereby resulting in significant maintenance costs. In addition, when a steel rules dives unevenly into the wood, the rule will tend to bend over sideways and become damaged. Attempts have been made to add a hard coating to the plywood substrate to prevent the rule from diving into it. While this helps, it does not solve the problem.
Attempts have been made to mount movable cavities with cross braces on top of wooden primary substrates. One such attempt is disclosed in WO 98/09781 to Geffros et al. The disclosed cutting knife assembly includes a plurality of cutting units with elongated strips serving as cross braces. Each cutting unit has a cutting rule and a plurality of cross members which include mounting holes for securing the cutting unit to the substrate. However, these cross members do not extend under the rule to prevent it from diving into the wooden substrate, nor do they distribute the forces applied to the rules during the cutting process over a widened surface area that is as large or larger than a cavity bounded by the steel rule. Instead, the forces remain highly concentrated along the lengths of the rule with some of the forces being transferred to the spaced cross members. Moreover, the portions of the rule that do not dive into the substrate can cause the rule to torque and deform. The elongated shape of the cross member makes the cross braced cutting units susceptible to deformation during the mounting and subsequent cutting operations, thereby effecting the quality of the final product. Consequently, the expensive and time consuming task of disassembling the die and replacing the. substrate will need to be performed on a frequent basis.
Another problem with the current dies using replaceable cavities is internal cutouts. Material is ejected out of the top of the tool rather than through the back of the tool, requiring frequent cleaning of scrap material from the cutting die. In addition the solid cutouts are not themselves movable with respect to the outer perimeter of the cavity, thereby making adjustments and changes difficult.
The steel rule die of the present invention includes cavities formed as cutting units that are separate from, and removably attached to a primary substrate. The steel rule die comprises a first substrate and a force distributing base plate, also referred to as a secondary substrate, positioned on the first substrate. The secondary substrate has a hardness which is greater than that of the first substrate. A length of rule with an upper cutting surface is secured to the secondary substrate for cutting objects. The secondary substrate extends along and is in contact with substantially the entire length of rule. The secondary substrate prevents the length of rule from diving into the primary substrate and requiring the premature, costly replacement of the primary substrate. The secondary substrate also distributes the forces applied to the length of rule during the cutting process over at least the surface area of the first substrate that it contacts so that they are not localized at any one point on the first substrate. The secondary substrate can be made out of steel or another suitable substrate material that is harder and denser than the material of the first substrate. The secondary substrate can be sized so that it extends slightly beyond the outer sidewalk of the steel rule. The steel rule can then be welded to the secondary substrate and the secondary substrate will form the lip that spaces adjacent cavities from each other.
The present invention solves the problem of accurately and consistently spacing adjacent cutting units from each other. The die according to the present invention comprises a substrate and first and second cutting assemblies positioned on the substrate. Each cutting assembly includes a force distributing secondary substrate, a length of rule secured to the secondary substrate and a spacing member extending in a direction away from its length of rule. The spacing members of the cutting units abut each other and space the lengths of rule a predetermined distance apart. The spacing members can include small extensions, or lips, of the secondary substrates or attachable spacers which extend around the periphery of the steel rule on each cutting unit to provide the desired, predetermined spacing between the adjacent rules so that material waste is reduced and scrap material does not become lodged between adjacent rules and damage them. The width of the lip around the periphery of the steel rule is one half the width of the desired space between the outer sidewalls of the rules of adjacent cavities, i.e., one-half the rule segment spacing. According to the present invention, when two spacing members are pressed into contact with each other, the steel rule of the adjacent cutting units are accurately spaced by the predetermined and desired rule segment spacing.
In another embodiment of the present invention, the steel secondary substrate is cut out to be the same size as the steel rule. In this embodiment, the rule is secured to the secondary substrate so that the forces applied to the rule during the cutting process are transferred to the second substrate and distributed over its surface area to prevent the rule and secondary substrate from damaging the first substrate. In this case, the secondary substrate would not be oversized and the cutting unit would not include a lip for spacing adjacent cavities from each other. In this embodiment, the spacing member would include an attachable spacer such as a tube, a wire or a gasket which is affixed around the periphery of each cutting, unit for providing a predetermined rule segment spacing between adjacent cutting units. The spacing member would have a width equal to one half the width of the desired, predetermined rule segment spacing between side surfaces of the adjacent rules. The spacing members of these embodiments ensure a consistent distance between adjacent cavities.
In another embodiment according to the present invention, the die comprises a substrate including at least one relief opening having a width for receiving scrap material. The die also includes a cutting assembly comprising a force distributing secondary substrate having an opening including a width for aligning with the relief opening in the substrate. A length of rule is secured to the secondary substrate and at least one cutting member is spaced from an edge of said secondary substrate by the length of rule and secured relative to the secondary substrate. The cutting member includes an upper cutting edge having an opening for communicating with the opening in the secondary substrate and the relief opening. The width of the relief opening is larger than the width of the opening in the secondary substrate so that scrap materials which pass through the cutting assembly will also pass through the relief opening without becoming lodged in the die.
The die according to the present invention also includes a substrate and a cutting assembly positioned on the substrate. The cutting assembly has a force distributing secondary substrate, a length of rule secured to the secondary substrate, and a plurality of openings in the secondary substrate. Each opening forms a fluid channel for exhausting air from within the cutting cavity. Moreover, these openings provide the manufacturer with visual markers and indicators for the location of a maker notch in the length of rule. Typically, the notch is vertically aligned with one of the openings in the secondary substrate.
It is an objective of the present invention to provide a multi-cavity die with cavities that can be moved relative to each other to allow cleaning of scrap material between cutting operations, wherein adjacent cavities are spaced by a consistent predetermined rule segment spacing.
It is a further objective of the present invention to provide a multi-cavity die wherein the cavities can be removed and replaced with cavities of different shapes.
It is a further objective of the present invention to provide a multi-cavity die wherein the cavities can be quickly and easily loosened or removed from their primary substrate and wherein the rule segment spacing between adjacent cavities will be precisely maintained when the cavities are replaced.
It is a further objective of the present invention to provide a multi-cavity die wherein the cutting units are attached to a secondary substrate in such a way as to increase the surface area which carries the load applied to the rule and, which is in contact with the primary substrate to prevent the rule from embedding into the primary substrate. At the same time, the present invention provides for a more rigid cutting unit that will not deform.
It is a further objective of the present invention to provide for internal cutouts that will allow for scrap material to pass through the die as well as being adjustable with respect to the cutting unit perimeter.